Sensorless BDCM Shaft Position Detection from Current Ripple
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Solution Overview
Problem
Existing systems for determining the position of a structure driven by a brushed direct current motor (BDCM) rely on external sensors, which increase complexity, weight, and power consumption.
Innovation Solution
An integrated circuit (IC) that isolates and amplifies the ripple waveform from the motor's current signal to determine the position of a movable structure coupled to the BDCM's shaft, eliminating the need for external sensors by using adaptive bandpass filtering and digital signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensors are used to determine the position of the mechanism, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines the motor driver circuit and position detection circuit into a single integrated circuit. The position detection circuit analyzes the commutation current signal from the BDCM to determine shaft position, eliminating the need for separate external sensors. This merging reduces device complexity while maintaining measurement precision through adaptive filtering and ripple waveform analysis.
Solution Approach 2:
The system uses the motor's own commutation current signal for position detection instead of requiring external sensors. The integrated circuit processes the current signal to extract position information, allowing the motor system to self-monitor its position without additional external components. This self-service approach reduces system complexity while maintaining accurate position measurement.
2Measurement precision
If external sensors are used to determine the position of the mechanism, then measurement precision is improved, but weight increases
Solution Approach 1:
The patent integrates the position detection functionality into the motor driver circuit, eliminating the need for separate external sensors that would add weight. The integrated circuit processes commutation current signals to determine shaft position, achieving accurate position detection without the additional weight of external sensor components.
3Measurement precision
If external sensors are used to determine the position of the mechanism, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The system uses the existing commutation current signal for position detection without requiring additional power-consuming external sensors. The integrated circuit processes this already-present signal to extract position information, achieving accurate measurement while avoiding the additional power consumption that would result from separate sensor systems.
4Measurement precision
If external sensors are used to determine the position of the mechanism, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple functions (motor driving and position detection) into a single integrated circuit, reducing the total component count and assembly requirements. This integration simplifies manufacturing processes and reduces costs compared to systems requiring separate external sensors, while maintaining accurate position detection through adaptive filtering and signal analysis.
Data Source
AI summary
Methods, circuits and computer program products are presented herein. The method includes isolating a ripple waveform from a current signal originating from a brushed direct current motor (BDCM). The method includes determining the wave count of the ripple waveform. The method includes determining a position of a movable structure operably coupled to a shaft of the BDCM according to the wave count of the ripple waveform. The present technology may be practiced without discrete capacitor components in high pass filtering aspects of the disclosed circuit. The methods, circuits and computer program products can be implemented to accurately determine a rotational position of a shaft of a BDCM and also position(s) of mechanism(s) coupled to the shaft without requiring any external sensors or other components for this purpose other than the disclosed circuits.